Linear actuator with improved indexing means

Abstract

The invention relates to a linear actuator (1) comprising: - an actuating rod (2) arranged in an outer tube (3) and capable of being moved linearly in a longitudinal direction (I-I) between a retracted position and an extended position; - an actuating member (4) comprising a threaded rod (5) that is rotatable about the longitudinal direction (I-I) and a nut (6) engaging with the threaded rod (5) by screwing, the nut (6) being mechanically coupled to the actuating rod (2); - means (7) for indexing the rotation of the nut (6) in the outer tube (3), including a first longitudinal groove (8) provided in the outer tube (3) and comprising two opposing lateral bearing paths (8a, 8b), and a first indexing member (10) rigidly connected to the nut (6). The first indexing member (10) comprises rollers which are each permanently pressed bearing against the two lateral bearing paths of the first longitudinal groove (8).

Description

LINEAR ACCURACY WITH IMPROVED INDEXING MEANS TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to linear actuators, and more particularly to the guidance of an actuating rod of a linear actuator.

[0002] A linear actuator AL according to the prior art as illustrated in the figure comprises: - an actuating rod TA arranged telescopically in an external tube TE and linearly movable along a longitudinal direction DL between a retraction position and at least one extension position relative to said external tube TE, - an actuating member OA (here a ball screw VB) shaped to generate the longitudinal movements of the actuating rod TA, comprising a threaded rod TF rotating about the longitudinal direction DL and a nut EC cooperating by screwing with the threaded rod TF to be moved bidirectionally in translation along the longitudinal direction DL by rotation of said threaded rod TF, said nut EC being mechanically coupled to the actuating rod TA, - indexing means MI for rotation of the nut EC in the external tube TE, shaped so as to lock the nut EC in rotation relative to the external tube TE.

[0003] In the linear actuator AL illustrated on the figure, the indexing means include: - two longitudinal grooves RL1 and RL2 formed in the external tube TE and each comprising two opposing lateral support paths, - two indexing members OI1 and OI2 integral with the nut EC and respectively engaged in guided translation between the two lateral support paths of the longitudinal grooves RL1 and RL2.

[0004] In practice, the indexing devices consist of pads made of a material with a low coefficient of friction in the longitudinal grooves.

[0005] To be mounted in the longitudinal grooves, the indexing members are inserted between the lateral support tracks of the corresponding longitudinal groove, and a lateral clearance must be provided between the indexing members and the lateral support tracks.

[0006] A first drawback is that the lateral play induces an inaccuracy in the longitudinal position of the nut when the threaded rod is rotated.

[0007] A second drawback is that the indexing elements wear out too quickly due to friction against the lateral support tracks. This premature wear increases the inaccuracy in the longitudinal position of the nut.

[0008] A third drawback is that lateral play can cause shocks (particularly when the threaded rod's direction of rotation is reversed), potentially leading to premature wear of the indexing components, especially when the linear actuator is used in high-frequency applications with high loads. This premature wear also increases the inaccuracy in the nut's longitudinal position.

[0009] These disadvantages are even more pronounced when the stroke of the indexing elements in the longitudinal grooves is very long, because the longer the stroke, the greater the lateral play in order to take into account the machining tolerances of the longitudinal grooves.

[0010] From document EP 2 886 908 A1, a linear actuator is known in which the position of the rollers can be adjusted via an eccentric sleeve so as to position the rollers in contact with the lateral bearing surfaces of the longitudinal groove. However, there is no permanent pressing of the rollers against the lateral bearing surfaces of the longitudinal groove. The adjustment thus made at a particular axial position of the longitudinal groove does not ensure permanent contact of the rollers against the lateral bearing surfaces of the longitudinal groove along its entire length, particularly if the width of the longitudinal groove increases relative to the specific axial position at which the roller positions were set due to machining tolerances.Furthermore, if the width of the longitudinal groove decreases relative to that of the particular axial position to which the roller positions have been set, there is overpressure on the rollers and the lateral support paths of the longitudinal groove, said overpressure being able to lead to premature deterioration.

[0011] From US patent 9,618,103 B2, a linear actuator is known according to the preamble of claim 1. The indexing element described therein has a significant size due to the addition of a lateral leaf spring. Furthermore, the pressing of the rollers against the lateral bearing surfaces of the longitudinal groove, achieved by means of the necessarily limited stiffness of the leaf spring, is insufficient to absorb, under high loads, the torque induced in the nut by the rotation of the threaded rod. This also results in an inaccuracy in the longitudinal position of the nut.

[0012] One problem proposed by the present invention is to provide a linear actuator with improved indexing means, exhibiting less inaccuracy in the longitudinal position of its nut, and reducing the risks of shocks and premature wear.

[0013] Simultaneously, the present invention aims to provide a linear actuator with indexing means having a small footprint and being able to easily have: - a stiffness high enough to reduce rotations and limit the risks of impacts against the lateral support paths of the longitudinal groove under the effect of the rotational torque induced in the nut by the rotation of the threaded rod, - a stiffness low enough to limit the risks of overpressure on the rollers and the lateral support paths of the longitudinal groove.

[0014] To achieve these and other objectives, the invention proposes a linear actuator comprising: - an actuating rod arranged telescopically in an external tube and linearly movable along a longitudinal direction between a retracted position and at least one extended position relative to said external tube, - an actuating member shaped to generate the longitudinal movements of the actuating rod, comprising a threaded rod rotating about the longitudinal direction and a nut cooperating by screwing with the threaded rod to be moved bidirectionally in translation along the longitudinal direction by rotation of said threaded rod, said nut being mechanically coupled to the actuating rod, - means for indexing the nut in rotation within the external tube, shaped to lock the nut in rotation relative to the external tube.and comprising: at least one first longitudinal groove formed in the outer tube and comprising two opposing lateral support paths, at least one first indexing member integral with the nut and engaged by sliding between the two lateral support paths of the first longitudinal groove, in which: - the first indexing member comprises a first pair of rollers substantially aligned longitudinally and having diameters less than the width between the two lateral support paths, - the first pair of rollers is carried by a first support element integral with the nut,- the first support element is shaped so as to permanently press a first roller of said first pair of rollers against one of said two lateral support tracks and the other roller of said first pair of rollers against the other of said lateral support tracks; according to the invention: - the first support element extends longitudinally in a first direction between a first end and a second end and extends transversely in a second direction between first and second lateral edges, - the first support element comprises at least one first arm extending along the first lateral edge towards a free end located in the vicinity of the first end, - said at least first arm comprises at its free end means for receiving a first roller,configured to receive a first roller in a rotational manner around a direction of rotation substantially perpendicular to the first and second directions, - the free end of said at least first arm can be moved in the direction of the second lateral edge by elastic flexing said at least first arm.

[0015] The actuation element can be a ball screw or any other helical linkage element operating on the screw / nut principle.

[0016] With the rollers constantly pressed elastically against their two opposing lateral tracks, the indexing element is received without lateral play in the first longitudinal groove, effectively limiting the risk of impact when the threaded rod's direction of rotation is reversed. This also increases the accuracy in determining the nut's longitudinal position based on the threaded rod's rotation (which can be determined using an encoder, for example).

[0017] The continuous elastic pressure of the rollers against the two opposing lateral raceways also compensates for manufacturing tolerances in the longitudinal groove, especially if it is long. Furthermore, it promotes rolling with little (or no) roller slippage against the lateral support raceways, thus limiting the risk of premature wear.

[0018] Such indexing means are compact. Moreover, said at least one arm can easily present (by a conformation giving it a suitable second moment of area): - a stiffness high enough to reduce rotations and limit the risks of impacts against the lateral bearing paths of the longitudinal groove under the effect of the rotational torque induced in the nut by the rotation of the threaded rod, - a stiffness low enough to limit the risks of overpressure on the rollers and the lateral bearing paths of the longitudinal groove.

[0019] Preferably, for more reliable, precise, and balanced indexing around the longitudinal direction, it may be provided that: - the indexing means include at least one second longitudinal groove formed in the outer tube and comprising two opposing lateral support tracks, - the indexing means include at least one second indexing member integral with the nut and slidingly engaged between the two lateral support tracks of the second longitudinal groove, - the second indexing member comprises a second pair of rollers substantially aligned longitudinally and having diameters smaller than the width between the two lateral support tracks, - the second pair of rollers is supported by a second support element integral with the nut.- the second support element is shaped so as to permanently press one roller of said second pair of rollers against one of said two lateral support tracks and the other roller of said second pair of rollers against the other of said lateral support tracks.

[0020] To further reduce the risk of premature wear, the rollers can advantageously be of the ball, roller or needle bearing type, with a coaxial inner and outer ring between which balls, rollers or needles are arranged.

[0021] Preferably, when an indexing element is disposed at rest outside the corresponding longitudinal groove, the rollers define between themselves a maximum width, taken transversely to their substantially longitudinal alignment direction, which is greater than the width of the corresponding longitudinal groove.

[0022] The mounting of the indexing element in the corresponding longitudinal groove is thus done in a state of pre-stress which guarantees good support of the rollers against the two opposing lateral support paths, and which considerably extends the life of said indexing element.

[0023] Advantageously, it can be provided that: - the first and / or second support element extends longitudinally in a first direction between a first end and a second end and extends transversely in a second direction between the first and second lateral edges, - the first and / or second support element comprises a first arm extending along the first lateral edge towards a free end located in the vicinity of the first end and a second arm extending along the second lateral edge towards a free end located in the vicinity of the second end, - each arm comprises at its free end means for receiving a roller configured to receive a roller in a rotational manner around a direction of rotation substantially perpendicular to the first and second directions,- The free end of the first arm can be moved towards the second lateral edge by elastic flexing said first arm, while the free end of the second arm can be moved towards the first lateral edge by elastic flexing said second arm.

[0024] Such a support element ensures that the indexing mechanisms behave identically regardless of the direction in which the actuating rod is moved. Furthermore, such a support element remains simple, inexpensive to manufacture, compact, and reliable.

[0025] Preferably, it can be provided that: - the elastic displacement capacity of the first arm towards the second lateral edge is provided by a slot made in the support element from its first end towards its second end, - the elastic displacement capacity of the second arm towards the first lateral edge is provided by a slot made in the support element from its second end towards its first end.

[0026] The elastic displacement capabilities of the first and second arms are thus achieved simply with a compact support element.

[0027] For an even smaller footprint, the slots can be made so as to present an overlap in the first direction.

[0028] Advantageously, the indexing element(s) are received in the respective longitudinal groove(s) by deformation of the first and / or second arms of the support elements. The arms of the support elements, tending to return to their initial position (before deformation), thus press the rollers against the lateral support tracks.

[0029] Preferably, the support elements are attached and fixed by means of a flange in their respective radial recesses formed in the outer wall of the nut. The flange allows the support elements to be fixed in a precise and constant orientation on the nut.

[0030] Advantageously, the linear actuator may include a first and a second longitudinal groove formed in the outer tube in diametrically opposite positions.

[0031] Preferably, each longitudinal groove can be defined by two opposing lateral rails attached and fixed within a longitudinal slot in the side wall of the outer tube. The lateral rails can be easily machined separately from the outer tube, thus with greater precision. The lateral rails can be made of a material less prone to premature wear and undergo finishes and treatments (particularly heat treatments) that provide them with greater wear resistance than the outer tube.

[0032] Alternatively, however, it can be envisaged that each longitudinal groove can be machined directly into the constituent mass of the outer tube.

[0033] To ensure reliable sliding of the nut in the outer tube, a guide ring can advantageously be provided between the nut and the inner surface of the outer tube, preferably two guide rings spaced apart along the longitudinal direction.

[0034] The guide ring(s) can preferably be made of a polymer material. For example, guide rings marketed under the name TURCITE® T59 by TRELLEBORG AB can be used. SUMMARY DESCRIPTION OF THE DRAWINGS

[0035] Other objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, made in relation to the accompanying figures, among which:

[0036] This is a longitudinal cross-sectional view of a linear actuator according to the prior art;

[0037] Laest is a longitudinal cross-sectional view of a particular embodiment of a linear actuator according to the present invention;

[0038] This is a perspective view of an external tube of the linear actuator in which a nut is guided in translation;

[0039] This is a perspective view of the external tube and the nut of the lapris in longitudinal section;

[0040] This is a longitudinal cross-sectional view of the outer tube and nut of the;

[0041] This is a partial, top view of the outer tube and nut;

[0042] This is a partial and bottom view of the outer tube and the nut of the;

[0043] This is a partial cross-sectional view of the external tube and nut according to a first transverse plane;

[0044] Laest is a partial cross-sectional view of the external tube and the nut according to a second cross-sectional plane;

[0045] This is a perspective view of a support element used in the embodiment of the;

[0046] This is a top view of the support element in a resting state;

[0047] This is a top view of the support element in a state of partial elastic deformation; and

[0048] This is a perspective view of a variant of a support element used in another particular embodiment of a linear actuator according to the present invention. DESCRIPTION OF PREFERRED METHODS OF IMPLEMENTATION

[0049] When identical numerical references are used in several figures, embodiments or variants of the invention, these numerical references designate identical or similar elements in each of the figures, embodiments or variants.

[0050] Schematic figures 2 to 12 illustrate a particular embodiment of linear actuator 1 according to the present invention (linear actuator 1 is only partially represented compared to the prior art linear actuator illustrated in the).This linear actuator 1 comprises: - an actuating rod 2 arranged telescopically in an external tube 3 and linearly movable along a longitudinal direction II between a retracted position and at least one extended position relative to said external tube 3, - an actuating member 4 shaped to generate the longitudinal movements of the actuating rod 2, comprising a threaded rod (externally) 5 rotating about the longitudinal direction II and a nut 6 (internally threaded) cooperating by screwing with the threaded rod 5 to be moved bidirectionally in translation along the longitudinal direction II by rotation of said threaded rod 5, said nut 6 being mechanically coupled to the actuating rod 2, - indexing means 7 for rotation of the nut 6 in the external tube 3, shaped to lock the nut 6 in rotation relative to the external tube 3.

[0051] The actuation element 4 is shown here only schematically. It could be a ball screw (as in the prior art) or any other helical linkage element operating on the screw / nut principle.

[0052] In the embodiment of figures 2 to 12, the indexing means 7 comprise: - a first longitudinal groove 8 formed in the external tube 3 and comprising two opposing lateral support paths 8a and 8b (see figures 8 and 9 more specifically), - a second longitudinal groove 9 formed in the external tube 3 and comprising two opposing lateral support paths 9a and 9b (see figures 8 and 9 more specifically), - a first indexing member 10 integral with the nut 6 and engaged by longitudinal displacement between the two lateral support paths 8a and 8b of the first longitudinal groove 8, - a second indexing member 11 integral with the nut 6 and engaged by longitudinal displacement between the two lateral support paths 9a and 9b of the second longitudinal groove 9.

[0053] The first indexing member 10 comprises a first pair of rollers 10a and 10b, offset longitudinally from each other and having diameters D10a and D10b less than the width L8 between the two lateral support tracks 8a and 8b. The first pair of rollers 10a and 10b is carried by a first support element 12 integral with the nut 6. The first support element 12 is shaped so as to permanently press the roller 10a in rolling contact against the lateral support track 8a and the other roller 10b in rolling contact against the other lateral support track 8b. As can be seen on the diagram, there remains a play J10a between the roller 10a and the lateral support path 8b, as well as a play J10b between the roller 10b and the lateral support path 8a.

[0054] Similarly, the second indexing member 11 comprises a second pair of rollers 11a and 11b, offset longitudinally from each other and having diameters D11a and D11b smaller than the width L9 between the two lateral support tracks 9a and 9b. The second pair of rollers 11a and 11b is supported by a second support element 13 integral with the nut 6. The second support element 13 is shaped so as to permanently press the roller 11a in rolling contact against the lateral support track 9a and the other roller 11b in rolling contact against the other lateral support track 9b. As can be seen on the diagram, there remains a play J11a between the roller 11a and the lateral support path 9b, as well as a play J11b between the roller 11b and the lateral support path 9a.

[0055] The support elements 12 and 13 are respectively attached to the nut 6 by means of a flange 20 or 21 in respective radial housings 22 or 23 provided in the outer wall of the nut 6 (figures 4 and 5).

[0056] As can be seen more particularly in figures 8 and 9, which are partial sections respectively along a first transverse plane P1 and along a second transverse plane P2, the rollers 10a, 10b, 11a and 11b are of the ball bearing type with an inner ring 14 and an outer ring 15 coaxial between which balls 16 are arranged. It is nevertheless possible to use rollers 10a, 10b, 11a and 11b of the roller or needle bearing type, or any other type of rotating roller.

[0057] Figures 10 to 12 show in particular that each of the first 12 and second 13 support elements extends longitudinally along a first direction II-II (intended to be parallel to the longitudinal direction II) between a first end 12a or 13a and a second end 12b or 13b, and extends transversely along a second direction III-III between a first 12c or 13c and a second lateral edge 12d or 13d. The first 12 and second 13 support elements comprise a basic body 26, substantially in the form of a plate extending along the first direction II-II and the second direction III-III.

[0058] The support elements 12 and 13 each have a first arm 12e or 13e extending along the first lateral edge 12c or 13c to a free end 120e or 130e located near the first end 12a or 13a. The support elements 12 and 13 also each have a second arm 12f or 13f extending along the second lateral edge 12d or 13d to a free end 120f or 130f located near the second end 12b or 13b.

[0059] Each arm 12e, 13e, 12f, or 13f has at its free end receiving means 17 for a roller 10a, 10b, 11a, or 11b, which are configured to receive a roller 10a, 10b, 11a, or 11b in a rotatable manner about a direction of rotation IV-IV or VV substantially perpendicular to the first II-II and second III-III directions. Here, the receiving means 17 comprise a tube 17a with an internal thread 17b. The tube 17a extends from and away from the base body 26 substantially perpendicular to the plane defined by the first direction II-II and the second direction III-III. Around the tube 17a, the inner ring 14 of the rollers 10a, 10b, 11a or 11b is fitted with a small clearance, and they are then held captive on their respective tube 17a by a screw 17c engaging in the internal thread 17b (see figures 8 and 9).

[0060] As is more particularly illustrated on the, the free end 120th or 130th of the first arm 12th or 13th can be moved elastically in the direction of the second lateral edge 12d or 13d, while the free end 120f or 130f of the second arm 12f or 13f can be moved elastically in the direction of the first lateral edge 12c or 13c.

[0061] The elastic displacement capacity of the first arm 12e or 13e towards the second lateral edge 12d or 13d is provided by a slot 18 formed in the support element 12 or 13 from its first end 12a or 13a towards its second end 12b or 13b. The elastic displacement capacity of the second arm 12f or 13f towards the first lateral edge 12c or 13c is provided by a slot 19 formed in the support element 12 or 13 from its second end 12b or 13b towards its first end 12a or 13a. The displacements of the free ends 120e, 130e, 120f, or 130f occur through elastic bending of the first arms 12e or 13e, or through elastic bending of the second arms 12f or 13f.

[0062] The stiffness of the 12th or 13th arm during its elastic displacement towards the second lateral edge 12d or 13d is easily adaptable by means of the distance separating the slot 18 from the lateral edge 12th or 13th.

[0063] The stiffness of the arm 12f or 13f during its elastic displacement towards the second lateral edge 12c or 13c is easily adaptable by means of the distance separating the slot 19 from the lateral edge 12d or 13d.

[0064] Slots 18 and 19 have an overlap R along the first direction II-II. This overlap R can be increased to provide the support elements 12 and 13 with an even smaller footprint along the first direction II-II.

[0065] On the, the arms 12th, 13th, 12f and 13f are not elastically displaced, so that the slots 18 and 19 have respective widths L18 and L19 substantially constant over their entire length.

[0066] Thus, when an indexing member 10 or 11 is disposed outside the corresponding longitudinal groove 8 or 9, the rollers 10a and 10b, or the rollers 11a and 11b, define between them a maximum width LM (), taken transversely to their substantially longitudinal alignment direction (first direction II-II), which is greater than the width L8 or L9 (or 7) of the corresponding longitudinal groove 8 or 9.

[0067] On the, the arms 12e, 13e, 12f and 13f are elastically displaced, so that the slots 18 and 19 have respective widths L18 and L19 which are not constant along their entire length. The rollers 10a and 10b, or the rollers 11a and 11b, then define between them a width L, taken transversely to their substantially longitudinal alignment direction (first direction II-II), which is less than or equal to the width L8 or L9 of the corresponding longitudinal groove 8 or 9: the indexing elements 10 or 11 can then be inserted into the corresponding groove 8 or 9.

[0068] In other words, the indexing members 10 and 11 are received in a compressed state in the respective longitudinal grooves 8 and 9 by deformation of the first arms 12e or 13e, and / or by deformation of the second arms 12f or 13f of the support elements 12 or 13. After insertion and fixing of the support elements 12 and 13, the elasticity of the arms 12e or 13e pushes the roller 10a or 11b against the lateral support path 8a or 9b, and the elasticity of the arms 12f or 13f pushes the roller 10b or 11a against the lateral support path 8b or 9a.

[0069] In the embodiment of figures 2 to 12, and as is particularly visible in figures 8 and 9, the longitudinal grooves 8 and 9 are delimited by two opposing lateral rails 80a and 80b on the one hand, and two opposing lateral rails 90a and 90b on the other hand, brought in and fixed in a respective longitudinal light 800 or 900 provided in the lateral wall of the external tube 3.

[0070] Alternatively, the longitudinal grooves 8 and 9 can be machined directly into the constituent mass of the side wall of the outer tube 3.

[0071] It can be seen in particular in figures 4 and 5 that guide rings 24 and 25 are arranged between the nut 6 and the inner surface 3a of the outer tube 3. The two guide rings 24 and 25 are spaced apart from each other in the longitudinal direction II.

[0072] The guide rings allow satisfactory coaxiality to be maintained between the nut 6 and the inner surface 3a of the outer tube 3.

[0073] As previously explained, the indexing members 10 and 11 are received in the respective longitudinal grooves 8 and 9 by elastic deformation of the first arms 12e or 13e, and / or by elastic deformation of the second arms 12f or 13f of the support elements 12 or 13. Thus, overall, there remains no lateral play between the first pair of rollers 10a and 10b transverse to the first longitudinal groove 8. Similarly, overall, there remains no lateral play between the second pair of rollers 11a and 11b transverse to the second longitudinal groove 9.

[0074] When the nut 6 slides in the outer tube 3, the respective indexing members 10 and 11 remain in constant contact (by rolling) with the lateral support tracks 8a and 8b on the one hand, and with the lateral support tracks 9a and 9b on the other, thanks to the elasticity of the arms 12e, 13e, 12f and 13f which allows the absorption of the geometric imperfections of the longitudinal grooves 8 and 9 and the damping of shocks during a reversal of the direction of rotation of the threaded rod 5. Simultaneously, greater accuracy is provided in determining the longitudinal position of the nut 6 when the threaded rod 5 is rotated.

[0075] The illustration shows a variant of support element 12 or 13 used in another particular embodiment of linear actuator 1 according to the present invention.

[0076] The support element 12 or 13 differs from that illustrated in figures 10 to 12 in that it comprises only one arm 12e or 13e extending along the first lateral edge 12c or 13c towards a free end 120e or 130e located in the vicinity of the first end 12a or 13a. The single arm 12e or 13e has at its free end 120e or 130e receiving means 17 for a first roller 10a or 11b, configured to receive a first roller 10a or 11b in a rotational manner around a direction of rotation IV-IV substantially perpendicular to the first II-II and second III-III directions. The free end 120th or 130th of the single arm 12th or 13th can be moved in the direction of the second lateral edge 12d or 13d by elastic bending of the single arm 12th or 13th.

[0077] The second roller 10b or 11a is received on receiving means 17 in a rotational manner about a direction of rotation IV-IV substantially perpendicular to the first II-II and second III-III directions. The tube 17a of the receiving means 17 for the second roller 10b or 11a extends from and away from a zone Z of the base body 26. Zone Z extends along the first direction II-II and is without a slot, in particular between the lateral edge 12c or 13c and the lateral edges 12d and 13d. Zone Z thus does not have a slot such as the slot 19 illustrated in Figures 10 to 12. The second roller 10b or 11a is therefore held in a fixed position relative to the base body 26, which is substantially in the form of a plate. In other words, the second roller 10b or 11a cannot be moved elastically in the direction of the first lateral edge 12c or 13c.

[0078] The single arm 12th or 13th is sufficient to induce an elastic and permanent pressing of the first roller 10a or 11b and of the second roller 10b or 11a against the lateral support paths 8a and 8b on one side or against the lateral support paths 9a and 9b on the other.

[0079] The operation of the lane support element 12 or 13, comprising only one arm 12e or 13e, is similar to that of the lane support element 12 or 13 shown in Figures 10 to 12, except that only one arm 12e or 13e deforms. However, the lane support element 12 or 13 does not exhibit identical behavior to the indexing members 10 and 11 in both directions of rotation of the threaded rod 5.

[0080] The present invention is not limited to the embodiments that have been explicitly described, but includes the various variants and generalizations contained within the scope of the following claims.

Claims

Linear actuator (1) comprising: - an actuating rod (2) arranged telescopically in an external tube (3) and linearly movable along a longitudinal direction (II) between a retracted position and at least one extended position relative to said external tube (3), - an actuating member (4) shaped to generate the longitudinal movements of the actuating rod (2), comprising a threaded rod (5) rotating about the longitudinal direction (II) and a nut (6) cooperating by screwing with the threaded rod (5) to be moved bidirectionally in translation along the longitudinal direction (II) by rotation of said threaded rod (5), said nut (6) being mechanically coupled to the actuating rod (2), - indexing means (7) for rotation of the nut (6) in the external tube (3), shaped to lock the nut (6) against rotation relative to the external tube (3).and comprising: at least one first longitudinal groove (8) formed in the outer tube (3) and comprising two opposing lateral support tracks (8a, 8b), at least one first indexing member (10) integral with the nut (6) and slidably engaged between the two lateral support tracks (8a, 8b) of the first longitudinal groove (8), wherein: - said at least one first indexing member (10) comprises a first pair of rollers (10a, 10b) offset longitudinally from each other and having diameters (D10a, D10b) less than the width (L8) between the two lateral support tracks (8a, 8b), - the first pair of rollers (10a, 10b) is carried by a first support element (12) integral with the nut (6), - the first support element (12) is shaped so as to press in permanent a first roller (10a, 10b) of said first pair of rollers (10a, 10b) in rolling contact against one of said two lateral support paths (8a,8b) and the other roller (10a, 10b) of said first pair of rollers (10a, 10b) in rolling contact against the other of said lateral support paths (8a, 8b), characterized in that: - the first support element (12) extends longitudinally in a first direction (II-II) between a first end (12a) and a second end (12b) and extends transversely in a second direction (III-III) between first (12c) and second (12d) lateral edges, - the first support element (12) comprises at least one first arm (12e) extending along the first lateral edge (12c) towards a free end (120e) located in the vicinity of the first end (12a), - said at least first arm (12e) comprises at its free end (120e) means for receiving a first roller (10a, 10b), shaped to receive a first roller (10a,10b) in a rotational manner about a direction of rotation (IV-IV) substantially perpendicular to the first (II-II) and second (III-III) directions, - the free end (120e) of said at least first arm (12e) can be displaced in the direction of the second lateral edge (12d) by elastic flexing of said at least first arm (12e). Linear actuator (1) according to claim 1, characterized in that: - the indexing means (7) comprise at least one second longitudinal groove (9) formed in the outer tube (3) and comprising two opposing lateral support tracks (9a, 9b), - the indexing means (7) comprise at least one second indexing member (11) integral with the nut (6) and slidably engaged between the two lateral support tracks (9a, 9b) of the second longitudinal groove (9), - the second indexing member (12) comprises a second pair of rollers (11a, 11b) offset longitudinally from each other and having diameters (D11a, D11b) smaller than the width (L9) between the two lateral support tracks (9a, 9b), - the second pair of rollers (11a, 11b) is supported by a second support element (13) integral with the nut (6),- the second support element (13) is shaped so as to permanently press a first roller (11a,11b) of said second pair of rollers (11a, 11b) in rolling contact against one of said two lateral support tracks (9a, 9b) and the other roller (11a, 11b) of said second pair of rollers (11a, 11b) in rolling contact against the other of said lateral support tracks (9a, 9b). Linear actuator (1) according to any one of claims 1 or 2, characterized in that the rollers (10a, 10b, 11a, 11b) are of the ball, roller or needle bearing type, with an inner ring (14) and an outer ring (15) coaxial between which balls (16) are arranged. Linear actuator (1) according to any one of claims 1 to 3, characterized in that, when an indexing member (10, 11) is disposed outside the corresponding longitudinal groove (8, 9), the rollers (10a-10b, 11a-11b) define between them a maximum width LM, taken transversely to their substantially longitudinal alignment direction, which is greater than the width (L8, L9) of the corresponding longitudinal groove (8, 9). Linear actuator (1) according to any one of claims 1 to 4, characterized in that: - the first and / or second support element (12, 13) extends longitudinally in a first direction (II-II) between a first end (12a, 13a) and a second end (12b, 13b) and extends transversely in a second direction (III-III) between first (12c, 13c) and second (12d, 13d) lateral edges, - the first and / or second support element (12, 13) comprises a first arm (12e, 13e) extending along the first lateral edge (12c, 13c) towards a free end (120e, 120f) located in the vicinity of the first end (12a, 13a) and a second arm (12f, 13f) extending along the second lateral edge (12d, 13d) towards a free end (120f, 130f) located in the vicinity of the second end (12b, 13b), - each arm (12e, 13e, 12f, 13f) has at its free end (120e, 130e, 120f, 130f) means for receiving (17) a roller (10a, 10b, 11a,11b), shaped to receive a roller (10a, 10b, 11a, 11b) in a rotational manner around a direction of rotation (IV-IV) substantially perpendicular to the first (II-II) and second (III-III) directions, - the free end (120e, 130e) of the first arm (12e, 13e) can be moved in the direction of the second lateral edge (12d, 13d) by elastic bending of said first arm (12e, 13e), while the free end (120f, 130f) of the second arm (12f, 13f) can be moved in the direction of the first lateral edge (12c, 13c) by elastic bending of said second arm (12f, 13f). Linear actuator (1) according to claim 5, characterized in that: - the elastic displacement capacity of the first arm (12e, 13e) in the direction of the second lateral edge (12d, 13d) is provided by a slot (18) formed in the support element (12, 13) from its first end (12a, 13a) in the direction of its second end (12b, 13b), - the elastic displacement capacity of the second arm (12f, 13f) in the direction of the first lateral edge (12c, 13c) is provided by a slot (19) formed in the support element (12, 13) from its second end (12b, 13b) in the direction of its first end (12a, 13a). Linear actuator (1) according to claim 6, characterized in that the slots (18, 19) are made so as to present an overlap (R) along the first direction (II-II). Linear actuator (1) according to any one of claims 5 to 7, characterized in that the indexing member(s) (10, 11) are received in the respective longitudinal groove(s) (8, 9) by deformation of the first (12e, 13e) and / or second (12f, 13f) arm(s) of the support elements (12, 13). Linear actuator (1) according to any one of claims 1 to 8, characterized in that the support elements (12, 13) are respectively attached and fixed by means of a flange (20, 21) in respective radial housings (22, 23) formed in the outer wall of the nut (6). Linear actuator (1) according to any one of claims 1 to 9, characterized in that it comprises a first (8) and a second (9) longitudinal grooves formed in the external tube (3) in diametrically opposed positions. Linear actuator (1) according to any one of claims 1 to 10, characterized in that each longitudinal groove (8, 9) is delimited by two opposing lateral rails (80a-80b, 90a-90b) attached and fixed in a longitudinal slot (800, 900) formed in the lateral wall of the outer tube (3). Linear actuator (1) according to any one of claims 1 to 10, characterized in that each longitudinal groove (8, 9) is machined directly into the constituent mass of the external tube (3). Linear actuator (1) according to any one of claims 1 to 12, characterized in that at least one guide ring (24, 25) is disposed between the nut (6) and the inner surface (3a) of the outer tube (3), preferably two guide rings (24, 25) spaced apart along the longitudinal direction (II). Linear actuator (1) according to claim 13, characterized in that the guide ring(s) (24, 25) are made of a polymer material.

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